The aim of this project is to better understand the biochemical structure and mechanism of replication of RNA Tumor Viruses. The ultimate goal is to understand the mechanisms of viral oncogenesis. The following approaches will be attempted during the year: 1. To study the genetic fine structure of the env, src, and c regions by heteroduplex mapping of various virus strains and their recombinants. 2. To study the biochemical structure of acute leukemia viruses by heteroduplex analysis, nucleic acid hybridization and in vitro translation. 3. To study the structure and mechanism of synthesis of DNA in vitro by DNA transfection and marker rescue.